This invention relates to an anti-reverse input clutch which transmits torque only from an input member to an output member and not from the output member to the input member.
Such an anti-reverse input clutch transmits torque applied to the input member in either direction to the output member but does not transmit reverse input torque applied to the output member to the input member. FIGS. 8A and 8B show a clutch having such a reverse input blocking function disclosed in Japanese patent publication 2-271116A. This clutch includes an input member 51 and an output member 52. A pin 53 secured to the input member 51 is inserted in a pin hole 54 formed in the output member with a slight clearance defined therebetween in the rotational direction. The clutch further includes a stationary outer ring 55 having a cylindrical inner surface radially opposed to the outer periphery of the output member 52, defining wedge-shaped spaces 56 therebetween which gradually narrow from the central portion thereof toward both circumferential ends. A pair of rolling elements 57 and an elastic member 58 are received in each wedge-shaped space 56 with the elastic member 58 disposed between the rolling elements 57. The clutch further includes a retainer 59 coupled to the input member 51 through the pin 53 and having legs 59a each inserted between a pair of adjacent wedge-shaped spaces 56. Driving and driven shafts (not shown) are inserted into the input member 51 and the output member 52, respectively, and coupled thereto through serrations.
Because the rolling elements 57 are biased toward the narrow portions of the respective wedge-shaped spaces by the elastic members 58, even if reverse input torque is applied to the output member 52, the rear one of each pair of the rolling elements 57 with respect to the rotational direction of the output member 52 engages the inner periphery of the outer ring 55 and the outer periphery of the output member 52, thus locking the output member 52, so that such reverse input torque is not transmitted to the input member 51.
When input torque is applied to the input member 51, the legs 59a of the retainer 59, which is rotationally fixed to the input member 51, push the rear one of each pair of rolling elements 57 with respect to the rotational direction of the input member 51 against the force of the elastic member 58, so that the rear one of each pair of rolling elements 57 disengages from the inner periphery of the outer ring 55 and the outer periphery of the output member 52. Thus, the rotation of the input member 51 is transmitted to the output member 52 with a slight angular delay.
In this anti-reverse input clutch, on the outer periphery of a large-diameter portion 60 at the axially central portion of the output member 52, cam surfaces 60a are formed which define the wedge-shaped spaces 56 in cooperation with the inner cylindrical surface of the outer ring 55. Thus, the output member 52 is complicated in structure and only limited options are available as methods for forming such an output member 52. It is therefore troublesome and thus costly to form such an output member, which will push up the manufacturing cost of the entire clutch.
An object of the present invention is to provide an anti-reverse input clutch of which the output member can be formed easily at a low cost.